This invention relates to a steering torque detecting device for detecting a steering torque caused by turning a steering wheel.
A conventional steering torque detecting device as shown in Japanese Patent Laid-open 63-78876 detects the reluctance produced by the relative rotation between the driving shaft and the steering shaft which are connected by a torsion.
In this related art, the relative rotation between the driving shaft and the steering shaft is detected as the steering torque. The torsion bar must be made smaller (narrower) than the driving shaft and the steering shaft to obtain a high sensitivity of torque detecting. In this case, the smaller (narrower) torsion bar can achieve an easy production of the relative rotation results in the high sensitivity of the torque detecting. This smaller (narrower) torsion bar, on the other hand, produced the low rigidity of axial direction and the radial direction causing the low durability. In order to increase the rigidity, some bearings have been used. Such bearings, however, cause hysteresis of the torque detecting.